It is known to form different machine-readable codes for different products. One manner is to form a code from an at least partly conductive material on a less conductive base material. For example, the code can be formed with conductive ink on paper or board. The conductive code can also in some cases be covered with another surface, which can be transparent or non-transparent.
Different solutions have been developed for reading a conductive code. One solution is presented in the U.S. Pat. No. 5,159,181, which discloses a capacitive code reader. The reader in question is based on identifying the conductive code in a capacitive manner with the electrodes of the reader, which electrodes are placed to correspond to the width of the code. Correspondingly, coupling areas are formed in the code at the locations of the electrodes of the reader. When the reader is at the location of the code, the electrodes of the reader and the code form a circuit and the alternating current (AC) between the electrodes is detected. In order for it to function reliably, the solution in question requires predefined mutual alignment of the code and the code reader, as well as precise reading direction. Because of this, it is mainly suitable for so-called card reader automatons, where the card comprising the code is brought to the reader aided by a motor. The solution does not operate reliably, for example, in such uses where the reader is moved in more unstable conditions e.g. by hand, in which case the speed, distance and/or direction in relation to the code may vary.